1. Field of the Invention
The present invention relates to the storage, in an integrated circuit, of a permanent binary code. The present invention more specifically applies to the writing, in the circuit manufacturing, of a permanent code intended to be read, upon use of the integrated circuit, to identify the circuit, or more specifically a circuit family.
2. Discussion of the Related Art
An example of application of the present invention is the authentication of an electronic element or assembly containing such an integrated circuit (for example, a smart card with or without contacts), in transactions or information exchanges with another element (for example, a card reading terminal). In such applications, it must be ensured that the integrated circuit is authentic and is not a pirate circuit or an emulated circuit. In particular, in the field of smart cards, it is currently difficult to fight against a large scale piracy consisting of manufacturing pirate cards (clones) identical to authentic cards, that is, integrating the same circuits made by similar technological processes.
Among these applications, the present invention more specifically relates to those where a permanent code common to several circuits is desired to be written. It may be, for example, an identifier of the manufacturer, an identifier of the original value of a prepaid count unit card (telephone unit cards), etc.
Memories or registers embedded in the integrated circuit are currently used to store this or these codes. The code is written in a non-modifiable manner in the storage element before or after manufacturing.
A disadvantage of such a technique is that it requires a visible programming, making the code detectable out of the circuit operation. Indeed, whether the code written upon manufacturing or by subsequent definitive programming, the fuse-type elements having been used for this writing are then visually identifiable. The progress made in terms of integrated circuit optical analysis then enables piracy of the code.
Another disadvantage of such a technique is that the subsequent circuit authentication, upon its use, requires a storage element read process, which takes time.